As a switching power-supply device capable of supplying relatively high power, a switching power-supply device that has a plurality of converter blocks and operates, in parallel, the converter blocks has been known.
Circuit constants of the converter blocks operated in parallel are typically the same. In this configuration, currents that flow through the respective converter blocks are the same, theoretically. However, actually, power that flows in the respective converter blocks are unbalanced due to non-uniformity of components configuring the circuits of the respective converter blocks.
Therefore, according to a switching power-supply device disclosed in JP-A-2005-33956, outputs of the respective converter blocks are smoothed by choke coils, and the choke coils are magnetically coupled to balance the powers flowing in the respective converter blocks.